1. Field of the Invention
The present invention relates to a method for controlling press working which comprises placing a work between upper and lower working wheels each rotatably supported by a horizontal shaft, and effecting relative movement between the work and the upper and lower working wheels to carry out working of a work, such as cutting, cutting a piece out, or drawing.
2. Description of the Prior Art
A method for working by means of a punching press machine using working wheels has previously been proposed in a Japanese Patent Application by the Applicant of the Present Application. Still, the method has been found to have problems to be solved.
Specifically, as schematically illustrated in FIG. 1, the punching press machine using working wheels comprises upper and lower working wheels 1, 6 including circular blades 2, 7 and circular stopper 3, 8 smaller in diameter than the circular blades 2, 7, respectively. The blade 2 and the stopper 3 are mounted on a common horizontal shaft 4 in contact with each other, and the blade 7 and the stopper 8 are mounted on a common horizontal shaft 9 in contact with each other. The upper and lower working wheels 1, 6 are vertically arranged in a cooperative manner, and a work W in the form of a plate is held therebetween. The working wheels 1, 6 and the work W are relatively moved in a direction which permits rotations of the working wheels, thereby effecting working of the work W such as cutting. Accordingly, the previously proposed punching press machine is capable of effectively carrying out working of a work such as cutting and cutting a piece out as compared with, for example, nibbling by means of a conventional punching press machine. On the other hand, however, the previously proposed punching press machine has been found to have the following problem due to the circular shape of the blade in its side view.
The problem is as follows. As schematically shown in FIG. 2, at an end Ce of a cutting line in cutting of a work W, boundary edges of a cut work Wc and the parent work W are still in engagement with the blades 2, 7 (shown in FIG. 2 by chain-dotted lines) of the working wheels 1, 6. Accordingly, if the parent work W in this condition is moved in a direction different from that of the cutting line, undesirable engagement between the work W and the blades 2, 7 of the working wheels 1, 6 is likely to be caused, leading to damage to the work W and the blades. This can be avoided by dissociating the working wheels 1, 6 from the surfaces of the work W, as shown in FIG. 2 by solid lines. However, if such dissociation of the working wheels 1, 6 from the surfaces of the work W is effected at the end Ce of the cutting line in parallel with the movement of the work W for the cutting, the working wheels 1, 6 cut the work W beyond the otherwise end Ce of the cutting line. This results in excess cutting to give rise to another problem.
Further, as well-known, it is considerably difficult in practice to cut a work along an arcuate cutting line having a small radius with blades (linear blades) having a certain length.
Moreover, in drawing by means of working wheels, the resultant therefrom has a shape which delicately varies between the starting point of the working at the beginning of the drawing and the endpoint of the working at the end of the drawing. Accordingly, if the drawing is carried out along a closed drawing course, the terminal of the drawing course at which the starting point and the endpoint of the drawing meet together is likely to be unsmooth in shape.
In addition, in deep drawing by means of working wheels, an amount of total draw depth of the deep drawing applied to a work by a ram (upper working wheel) is large. Accordingly, if the deep drawing is performed to the draw depth at one stroke, a clamp holding a work is likely to come off for protecting the equipment from overloading. Under the existing circumstances, to avoid this, a program is prepared according to which the same working (drawing) steps are repeated with a small amount of draw depth in each working step applied by the ram, thereby carrying out deep drawing. However, if deep drawing is carried out in this manner, programs of the same contents must be written over a plurality of working steps. Further, a tact time of the working is unavoidably long.